I. Field of the Invention
This invention relates to novel carbon beads, a process of producing the same and a liquid chromatography column containing the carbon beads as a packing.
II. Description of the Related Art
High performance liquid chromatography (HPLC) is a system with which a sample is separated by a chromatography column by passing a mobile phase solvent through the column with applied pressure and the eluted fractions are continuously monitored with a detector. In the last decade, HPLC has spread widely because it can be used in a wide variety of fields for analyzing wide variety of substances. Since HPLC has made it possible to analyze naturally occurring organic compounds and body components, which was conventionally difficult, HPLC has been practically employed in clinical tests, analysis of pharmaceuticals and toxicity tests, and has been rapidly developed.
Conventionally, silica-based packings and organic polymer-based packings (porous polymers) are used as packings of HPLC columns. However, silica-based packings have a drawback in that the chromatography is likely to be influenced by the silanol groups on the surfaces of the packings. As for the organic polymer-based packings, although they are insoluble in any solvent because they are crosslinked, they are swelled by their good solvents, that is, the solvents which dissolve the corresponding non-crosslinked polymers. Thus, in the HPLC in which an organic polymer gel is used as the stationary phase, exchange of solvents is usually difficult. Further, since the pressure resistance of the stationary phase is not sufficient, the flow rate of the eluent is limited.
Thus, it is desired to develop a packing for HPLC which can overcome the drawbacks of conventional HPLC packings. Carbon-based packings are expected as good candidates because they are resistant to swelling or shrinking and they are resistant to acid and base. It is important that a packing for HPLC should have the following properties:
(1) It is hard enough to withstand high pressure. PA1 (2) It is stable during operation and storage. PA1 (3) It suitably retains solutes. PA1 (4) It has a uniform surface. PA1 (5) It has an appropriate pore size. PA1 (6) It is easily prepared.
Guiochon et al proposed a thermally decomposed modified carbon black prepared by vapor-depositing a thermally decomposed product of benzene on carbon black, and succeeded in synthesizing a carbon-based adsorbent (J. Liq. Chromatogr. 119, 41 (1976); J. Liq. Chromatogr., 12, 233 (1976)). However, this carbon-based adsorbent has drawbacks in that its capacity is small and the reproducibility of the chromatography using the adsorbent is low. Smolkova et al examined effectiveness of using a reduction product of polytetrafluoroethylene prepared by reducing it by lithium amalgam at room temperature (J. Liq. Chromatogr., 119, 61 (1980)). Zwier and Burke examined the effectiveness of surface chemical modification of fluoropolymer derivative by the reduction of Kel-F300 by lithium amalgam and by surface modification by a Grignard reagent (Anal. Chem., 53, 812 (1981)). Ciccioli et al examined the effectiveness of using a commercially available carbon black which is in the form of graphite (J. Chromatogr. 269, 47 (1983)). Unger et al examined the effectiveness of using cokes and active carbon (J. Chromatogr., 202, 3 (1980). Hagiwara et al examined the effectiveness of using mesophase carbon microbeads (Abstract of 7th Carbon Material Chemistry Association 70 (1980), Mol. Cryst. Liq. Cryst., 94, 97 (1983); Japanese Laid Open Patent Application (Kokai) Nos. 56-44846 and 58-41351). However, the chromatography packings of the pulverized type prepared by finely pulverizing these porous carbon material, the packings of the surface modified type prepared by coating gel surfaces with carbon or the packings of the crystal sphere type have drawbacks in that the size of the pores in the packings cannot be optionally controlled and the crystal state from amorphous to graphite cannot be chosen. Thus, it is practically impossible to employ these materials as packings of HPLC.